A single proton has a charge of +1.602 x 10^-19 Coulombs. An atomic nucleus is composed of protons and neutrons, and the nucleus is orbited by electrons.

A single electron has a charge of -1.602 x 10^-19 Coulombs, a negative charge which exactly cancels the positive charge of one proton. The number of protons contained in the atomic nucleus is different for each chemical element. In fact, the number of protons in the atomic nucleus defines the type of atom. A hydrogen atom, for example, has atomic number 1, meaning its nucleus contains one proton (sometimes accompanied by a neutron in deuterium, or heavy hydrogen, but neutrons do not carry a charge--they just contribute mass), and the atom remains charge neutral when a single electron orbits the nucleus.

The total charge of all the protons in the hydrogen nucleus is given by 1 x 1.602 x 10^-19 Coulombs. Atomic number 2 is helium, with a nucleus containing two protons and two neutrons. The total charge of a helium nucleus is 2 x 1.602 x 10^-19 Coulombs = 3.204 x 10^-19 Coulombs. What about an oxygen nucleus? Hint: oxygen is atomic number 8.

As a note, charge may also be expressed in elementary charge units (e). 1e = 1.602 x 10^-19 Coulombs, so the charge of a hydrogen nucleus is +1e and the charge of a helium nucleus is +2e.